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Engineered Landfill Site – Cintec Environnement Inc.

The management of municipal solid wastes is one of the most important challenges faced by our urban and industrial societies. If sanitary landfilling of waste produced by the population, public and private institutions, businesses and industries is a common practice in industrialized countries, it has barely been initiated in underdeveloped ones.

There, huge quantities of wastes are managed inadequately in unprotected and uncontrolled dumps. This management does not take into account environmental and social realities. These practices :

  • Constitute a danger to public health;
  • Affect the quality of the environment by risking the pollution of groundwater, surface water, the air and soil;
  • Jeopardize residential development in the vicinity of these sites as well as the regional planning;
  • Waste renewable resources.

With over 15 years experience in the field of secure landfilling of contaminated soil, the Cintec Group has exported its know-how in some under developped countries and is on its way in doing same in other ones by designing and building engineered landfill sites adapted to each country’s environmental, economical and social conditions and regulations.

Nejapa, El Salvador

 “El Guayabal”, Venezuela

Description of the technology

An engineered landfill site allows final disposal of solid waste in a secure manner by minimizing the impacts on the environment. The design of the landfill site proposed by the Cintec Group uses leading-edge technology and the materials used for the construction of the cells have proven their long-term stability.

The waste is spread out in a thin layer in the waterproof cells where they are leveled, compacted and covered periodically with soil or another inert material. Ditches all around the site deviate the surface water before it comes in contact with the waste. As for rainwater that infiltrates itself into the waste, it gets mixed with contaminants and increases leachate, which is collected at the bottom of the cells and is sent to the lagoons for treatment. After a few years, the degradation of the biodegradable part in waste produces landfill gas. This gas is captured by a network of wells installed all over the site and is burned or converted into energy.

Once their final capacity is attained, we proceed with the closure of the cells by installing a cover that will favour the growth of vegetation. During the operation and after the closure of the cells, an environmental follow-up program is put in place in order to verify the quality of the surface and underground water, the quality of the air, the noise level and the efficiency of the systems for leachate treatment and landfill gas control.

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The use of this technology for final disposal of waste has significant advantages. It is a final disposal method, whose initial investment and operation costs are low compared to other methods of elimination such as incineration.

The use of geomembranes in the construction of cells assures impermeability thus avoiding any possible contamination of the soil as well as the superficial and underground water. The periodical covering of the wastes reduces odours and prevents proliferation of vermin, thus diminishing propagation risks of infectious diseases.

In addition to the collection network and leachate treatment facilities, the Cintec Group incorporated a leachate circulation system, which facilitates compaction and accelerates the waste’s degradation process.

The collection equipment and the possible benefits of landfill gas show that waste is not just harmful residue but can also become an interesting resource for the production of energy. For example, a thermal station supplied with landfill gas produced in a landfill site containing 35 million metric tons of waste can produce the necessary electrical energy to supply about 10,000 homes.

The construction of engineered landfill sites is not carried out without any constraints. The following are among a few :

  • In areas densely populated, the availability of lands suited for landfilling is often limited; engineered landfill sites require a large surface area.
  • Topographical, geotechnical and hydrogeological conditions as well as town planning rules are also constraining elements in choosing a location for an engineered landfill site; for example, it is necessary to reserve a buffer zone between the site and the neighboring residences and distances must also be respected regarding facilities such as airports, sources of drinkable water and rivers.
  • Social acceptance for the construction of this type of facility is often very difficult and sometimes even impossible to obtain.

Installation and operation
The main steps for the construction of Cintec Group’s engineered landfill sites require the following operations and facilities :

  • Preliminary studiesThe construction work on the site does not start until a hydrogeological study has made it possible to define the location of the ground water, the depth, the permeability of the soil or rock, thus confirming that adequate conditions have been met to build the site of which the landfill cells is a part.
  • Landfill cellsThe construction of the cells involves large volumes of excavation and backfill. The slope of the walls and of the bottom of the cells are excavated with precision and leveled with the greatest care so that the multilayered system which rests on these surfaces will be effective and will not be damaged.- At the bottom of the excavation there is a layer of compacted clay of at least 60 cm.- We then place a waterproof geomembrane made of high density polyethylene (HDPE) 1.5 mm thick.- The entire surface of the geomembrane is covered with a protective goetextile.- A draining layer of gravel completes the multilayered system.

The geomembranes are made of materials well-known for their impermeability, their high resistance to a vast range of chemical compounds, and their remarkable mechanical properties. In order to avoid perforation or defective welding, a quality assurance and quality control program is set up during the installation of the geomembranes.

Collection and treatment of leachate

To collect and prevent the accumulation of leachate water, a pipe network is installed at the bottom of cells. The system consists of perforated pipes made of high-density polyethylene (HDPE). These pipes are installed in ditches and later covered with gravel and a filtration geotextile to minimize possible risk of obstruction.

The liquid from the leachate is stored and treated in lagoons adjacent to the landfill site. The degradation of organic contaminants contained in the leachate is achieved through bacterial activity. To ensure the growth of bacteria, fertilizers including phosphate, nitrogen and potassium are added to the leachate. Aerators are installed to provide oxygen for the bacteria.

Following the treatment, which takes approximately 45 days, the leachate is disinfected and the water can be released to the local drainage system, used as irrigation water or to facilitate compaction and speed up degradation and stabilization of the compacting waste.


Surface water drainage network

Rain water is intercepted before it comes into contact with wastes in such a way that it does not drain into the landfill cells. It is directed, via ditches and ducts, towards an external drainage network so that the quantities of leachate collected during the operation of the landfill site are reduced to a minimum.

Collection and valorization of landfill gases

For the collection of landfill gases, composed mainly of methane and carbon dioxide, Cintec Group’s engineered landfill sites are equipped with a network of vertical wells, regularly spaced in the interior of the cells and are prolonged up until the final covering layer. These wells are connected to horizontal tubes that lead the landfill gas to a burning station that use torches or go to an energy valorization station, if such facility is economically viable.

Control measures

In engineered landfill sites, many control measures exist in order to limit the inconveniences for the neighboring population: installation of paper trap fences around the front of the waste compaction, regular cleaning of the access road and of surrounding areas, watering of the roads to limit the emission of dust, fumigation operations to prevent the proliferation of insects infested with germs.

Multilayered roof

When the cell has reached its final elevation, it is covered by a composite protective roof consisting of :
– a first layer of backfill material, of 30 cm;
– an impermeable geomembrane;
– a second layer of backfill;
– a final layer of organic soil to favour the growth of vegetation.

Scale, administrative offices and utilitary buildings

A scale and a sentry box are found at the entrance of the site. All trucks are verified and weighed before they are unloaded. A computerized data recording system is on site. The administrative offices and utilitary buildings, such as a warehouse, a workshop, service areas for the employees and a laboratory are also part of the engineered landfill site.

Environmental follow-up

The objective of the program is to ensure that the activities carried out at the site do not have an adverse impact on the environment and the quality of life of the neighboring population. The program also defines the necessary measures that need to be taken should the results of the study not meet the required quality parameters. During the exploitation and after the closing of the cells, an environmental follow-up program is implemented to verify the quality of the surface water and underground water, the air’s quality, the level of noise as well as the efficiency of the systems for leachate treatment and landfill gas collection.


The construction of an engineered landfill site requires an important investment, which generally implies the necessity of a minimal exploitation period of about 20 years.

In addition to the length of the exploitation period, the costs can vary pending the quantity treated and the application of the other sections of the integral management plan, for which the Cintec Group is responsible (collection, construction/exploitation of transfer and sorting stations, access roads, education and awareness programs …).

Additional information

The Cintec Group has the technical expertise to design, build and operate engineered landfill sites. The Cintec Group can also build facilities to treat biomedical wastes and/or a factory for the cogeneration of electricity from landfill gases, should these services be required in the host countries.

The Cintec Group can also get involved in everything revolving the construction of access roads and infrastructures, the closing and rehabilitation of former dumpsites, preliminary studies and studies on environmental impacts as well as on the social issues, whether it’s education/awareness or social reintegration of the people whose survival depended on sorting through the resources of former dumpsites.

Cintec Environnement Inc.
5505 Irwin
Lasalle, Québec, H8N 1A1

Phone :    (514) 368-4861
Fax :    (514) 368-4669
Email :    cintec1@cintec.ca
Web site :    www.cintec.ca